The present invention relates to a device for changing and releasing or clamping in the tool in tool systems in which a tool head and a tool holder are connected together by means of a clamping unit. The invention relates, in particular, to such tool systems in which the clamping screw of the clamping unit is integrated in the tool holder.
For such machine tools, too changing devices are known in which a gripping element takes the tool out of the basic tool holder and inserts a new one. A clamping unit installed in the machine tool releases and clamps in the tool. Releasing and clamping in of the tool are effected manually.
U.S. Pat. 4,581,811 discloses a tool changing device in which the clamping screw is operated by an automatic device stationarily attached to the machine tool. The machine tool is provided with a tool holder receptacle having a central bore into which a tool holder can be inserted, the tool holder being equipped with a cylindrical section for engagement of a changing arm. The tool holder is connected with the tool receptacle by means of a clamping unit including a clamping screw. The cylindrical section of the tool holder is equipped with a radial, threaded bore. At the free end of a changing arm which operates independently of the machine tool, there is disposed a motor-driven connecting bolt which is provided with an external thread matching the threaded bore of the cylindrical section of the tool holder. To change the tool, the connecting bolt of the changing arm is automatically screwed into the radial, threaded bore of the tool holder. The threaded bore and the connecting bolt are connected together in the correct position by way of prism-shaped centering recesses provided at the outer end of the changing head. A motor-driven screwdriver stationarily provided at the machine tool loosens the clamping screw in the tool receptacle. The tool is removed by the changing arm and an identical changing head disposed on the changing arm diametrally opposite the old tool head is attached. Then the screwdriver tightens the clamping screw again.
It is a drawback of this device that the exchange and release or tightening of the tool is performed by means of two separate devices. Not all machine tools provide sufficient space for a screwdriver to be attached stationarily on the machine. Another drawback of the above-described tool changing device is that right and left tool arrangements require appropriately adapted embodiments of this device. Thus, this tool changing device is not universally usable. Finally, it is a further drawback of the system that the changing arm provides no more than two locations for changing heads. Thus, for machine tools having tool receptacles able to accommodate a plurality of exchanging heads, the tool change times are lengthened considerably.